54 A. F. Rogers — Baddeleyite from Montana. 



ble to all possible nephelites. The decision falls upon the 

 three components NaAlSi0 4 , KAlSi0 4 , and NaAlSi 3 8 , sug- 

 gested by Schaller. 



4. Conclusions are drawn as to when nephelite may be 

 expected to be saturated with silica. 



Mineralogical Laboratory, 



Massachusetts Institute of Technology, Boston. 



Art. IX. — Baddeleyite from Montana ; by Austin F. Rogers. 



On some corundum specimens from Montana, obtained from 

 Ward's Natural Science Establishment, the writer noticed a 

 black submetallic mineral. The nature of the mineral was 

 not evident at sight, but it was soon identified by physical and 

 chemical tests as baddeleyite or native zirconia, Zr0 2 . 



Baddeleyite is a very rare mineral, first described from the 

 gem-bearing gravels of Ceylon by Fletcher. - It had also been 

 found in decomposed jacupirangite (magnetite-pyroxenite) at 

 Jacupiranga, Sao Paulo, Brazil, and was called brazilite by 

 Hussak,f w T ho later J withdrew his name in favor of baddeley- 

 ite. Hussakg has also described baddeleyite from Alno, 

 Sweden, where it occurs in magnetite-olivine segregations in 

 nephelite-syenite. 



The specimens obtained of Ward's were from Montana, but 

 the exact locality was not stated. Similar specimens contain- 

 ing baddeleyite purchased from Mr. R. M. Wilke of Palo Alto, 

 California, are from the property of the Bozeman Corundum 

 Company, which according to Pratt] is fourteen miles south- 

 west of Bozeman, Montana. 



Occurrence. — The baddeleyite is an accessory constituent of 

 a gneissoid corundum-syenite containing microcline-microper- 

 thite, biotite, and corundum, with subordinate amounts of mus- 

 covite, sillimanite, and zircon. It occurs in minute crystals 

 and rounded blebs with a maximum size of about 3 mm . The 

 baddeleyite is found in both the feldspar and the corundum, 

 but is especially abundant on the surface of the corundum, and 

 often adheres to the feldspar when the corundum crystals are 

 broken out of the matrix. 



* Mineralogical Magazine, vol. x, p. 148, 1893. 

 fNeues Jahrb. Min., 1892, vol. ii, p. 141. 

 iMin. Petr. Mitth., vol. xiv, p. 395, 1895. 

 SNeues Jahrb. Min., 1898, vol. ii, p. 228. 

 (Bull. 269, U. S. G. S., p. 133, 1906. 



